The present invention relates generally to media communications among sites of an optical communication system.
Modern optical communication links increasingly extend over great distances, e.g., thousands of kilometers. Optical links of such reach typically are divided into multiple spans with optical amplification equipment placed between the spans. Optical add/drop multiplexers to remove and substitute optical channels are also often distributed throughout the link. Equipment requiring supervision and maintenance is therefore found at the transmit end of the link, at the receive end of the link, and at many amplification sites in between.
Like in many communication systems, configuration, diagnosis, and repair of the link often involve coordination in real time among personnel at two or more remotely located sites. It is especially desirable for the personnel to communicate by telephone. Intermediate amplification sites are, however, often found in remote areas where there is no ready connection to the public telephone network. These sites are often outside cellular telephone coverage areas. Even if the site itself is located in a wireless coverage area, the specific location of the optical equipment will often be in a shielded subterranean area.
A need thus arises to somehow utilize the optical communication link, which is optimized for throughput of very large volumes of data, to exchange voice telephone signals between sites as desired. Various prior art approaches have been developed that make use of a wavelength dedicated to management functionality and referred to as the Optical Supervisory Channel (OSC). In one approach, a 64 Kbps digital channel is established in reserved bytes of the OSC and specialized equipment is used to translate between analog telephone signals and the format required by the special digital channel. The specialized equipment is both very expensive and bulky. Also, certain services such as call waiting, call forwarding, on-line directory, voicemail message display, etc., cannot be accommodated.
An alternative approach is to equip each site with an IP (Layer 3) router and a voice over IP (VoIP) telephone or combination of analog telephone and VoIP router card. Due to the expense of the router, this approach can also be quite expensive and can consume considerable space. Furthermore, conference calls can only be accommodated by way of a difficult capacity-increasing modification to the modem that implements the optical service channel, since the bandwidth requirements for a conference call are roughly proportional to the number of connected users (sites). Improved systems and methods for voice connectivity among WDM sites are needed.